Some Like It Hot
Using a heat gun, Mark Ashton warms the surface of the boat before photographing it with his IR camera.
To many surveyors and their clients, the moisture meter is the ne plus ultra of laminate-testing tools, a technical leap and a half beyond whacking the boat with a soft-faced hammer. But not for long: Moisture meters are so 20th century. Today cutting-edge surveyors are using expensive infrared cameras along with traditional surveyors' tools. Colorful IR, or thermographic, images provide trained interpreters more detailed, more accurate information than a meter can and in a graphic format that paints an at-a-glance picture of the laminate's condition. And while anybody with a few hundred bucks can buy a moisture meter and call himself a surveyor, IR equipment is expensive (they start at around $6,700) and requires extensive training to use, so only serious, experienced pros are likely to make the investment. One who has is Mark Ashton of Independent Marine Systems, a surveyor specializing in composite construction.
Using his Raytheon Pro 400 Digital IR camera (it looks like a camcorder with a PDA mounted on top and can shoot both video and stills), Ashton observes and records a hull thermographically, one section at a time. Voids, moisture, delaminations, and other anomalies heat and cool at different rates than laminate in perfect condition and therefore show up differently over time on the infrared images; wet areas cool more slowly than dry areas, for example, and voids appear hotter. Thermography gives Ashton a kind of "X-ray vision" so he can analyze the state of a laminate more accurately and with more confidence than if he used only traditional tools. (Ashton also carries a moisture meter and the surveyor's standby, a hammer for sounding the hull.) Thermography is the most accurate nondestructive method of inspecting laminates, at least with today's technology, he explains.
How does it work? Any object produces infrared energy relative to its temperature—the hotter the object, the more IR it produces. But like X-rays, microwaves, and radiowaves, IR is invisible to the human eye, so we need a little help: Thermographic infrared cameras are engineered to interpret infrared energy and produce an image using temperature, not light, as a scale. A conventional camera, whether film or digital, reads visible light. Yes, film cameras can use infrared film, but it records a combination of visible light and some reflected IR as well; it's not the same as thermography. "Night vision" goggles or cameras amplify small amounts of visible light, but that's not thermography, either.
In the hands of an expert, an IR camera is a valuable tool for a wide range of applications. Locating heat or air-conditioning losses in a building are examples, or inspecting high-voltage electrical equipment: Poor connections increase resistance and create more heat than good connections. Thermography can detect roof leaks and identify water-damaged areas, inspect boilers and furnaces, locate low-intensity forest fires before they burst out of control, help find lost hikers and campers by detecting their body heat, and even aid in evaluating and treating injuries and diseases in both humans and animals. The aviation industry uses IR to detect water intrusion and laminate condition of composite parts of airplanes. Thermography is the only way to inspect carbon-fiber laminates—moisture meters won't work on carbon—so it's the favored technique for surveying racing sailboats, which float on hulls and under masts made of that material. In the marine industry thermography is often used to survey a vessel in need of repair due to composite failure or accident.
In thermography, at least as applied in marine applications, "absolute temperature usually isn't important," Ashton explains; it's changes in temperature, and the rate of change, that he observes. The change in temperature of the hull can come from natural means—the sun coming up or going down if the boat's outside—or artificial ones. In fact, Ashton often uses an external heat source to warm the hull so slightly that it's barely noticeably to the touch, then watches it cool over a controlled time on the sensitive IR camera. Sometimes he even warms the boat from the inside, using electric heaters. The method depends on the situation, but the images seen from a direct external heat source are the most dramatic.
As the hull cools, Ashton watches the colors change on the Pro 400's LCD, snapping stills frequently; a typical thermo survey results in hundreds of pop-art-colored digital IR photos captured on removable storage media. Back in his office, he downloads the pictures to his computer and interprets them with the help of sophisticated software. He can change the color palette on any image to make certain features or problems stand out more clearly or even convert it to grayscale. His final survey report will include a selection of photos, each one interpreted in a caption so the client can understand what the colors mean, with a conventional digital image next to it as a reference. Ashton often uses a graphics program to draw on the images and highlight problem areas.
Most of Ashton's clients prefer not to share his findings with other folks, especially writers—heck, they probably want to sell their boats, not tell the world what's wrong with them—but I was cleared to attend a thermographic survey of a 25-foot sportfisherman that's 20 years old but was built to the top standards of the time. The owner liked the boat enough to invest in renovating her but wanted to know what he was getting into before starting. As Ashton heated each section of the hull, I watched the IR image change on the camera's PDA display. The color changes, reflecting the hull's cooling, were obvious, but figuring out what the changes meant took experience.
Some things were clear, though: At one point, the individual blocks of coring were visible, the temperature of the core itself different from that of the adjacent filler. Solid areas of the hull were also obvious, such as around through-hull fittings, as were long-forgotten repairs. We saw no delamination, no large voids, no resin-starved areas—but, ominously, along the keel for the aft two-thirds of the boat's length was a dark patch, signifying water in the sandwich. Ashton said he'd recommend cutting a couple of samples from this area to see precisely what was going on and to help in planning the repair. Using the report from our investigation, the hull was evacuated of moisture and infused with resin to fill the area the moisture had occupied. The hull was then reevaluated with the IR camera to ensure the repair was complete.
Interpreting IR images takes training and practice. Ashton is a SAMS-accredited marine surveyor and holds a Level I thermographer certification from the Infrared Training Center (ITC) in North Billerica, Massachusetts, a subsidiary of FLIR Systems, manufacturers of IR cameras. The ITC gives its Level I course in many cities throughout the U.S. and Canada; it covers the fundamentals of IR thermography, but it isn't a basic course. During the four-day program, students learn the principles of thermal science, heat transfer, and infrared science, along with electrical, mechanical, and building applications of thermography. According to ITC director Bob Madding, although "a couple of handfuls" of marine surveyors have reached Level I certification, there isn't enough demand, yet, for a specific course. However, he adds, marine surveying uses many of the same principles as thermography of buildings and electrical systems. "You have to know as much about what you're looking at as what you're looking at it with," he says; it's easier to teach an experienced marine surveyor how to incorporate an IR camera into his practice than it is to teach a camera expert how to be a surveyor. But, Madding adds, there are lots of applications for IR imaging for marinas, service providers, and even yacht owners. Thermography is a great tool not only for surveying hulls, but also for troubleshooting electrical problems, monitoring heat-exchanger and turbocharger temperatures, or even checking the condition of shore cords and plugs.
Thermography is just too cool a 21st-century technology to ignore. Once the prices come down (Ashton's camera cost about $15,000), as I expect they will, every serious surveyor will have an IR camera in his bag, and no client will accept a survey report without lots of colorful infrared images. Today it'll take some searching to find a surveyor with thermographic capabilities (see contact information below for SAMS), but if your boat needs a thorough inspection with minimal application of the hole saw, you'll find it worth the effort.
Independent Marine Systems
Society of Accredited Marine Surveyors
This article originally appeared in the September 2006 issue of Power & Motoryacht magazine.